Rotary speed-change-sensing mechanism



April 21, 1970 M. K. RICHMOND Rm 26.352

ROTARY SPEEDCHANGE-SENSING MECHANISM Original Filed May 10, 1962 ZSheetS-Sheet I.

INVENTOR. Moscow A. flex/Mafia April 21, 1970 RICHMOND Re. 26,862

ROTARY SPEED-CHANGE-SENSING MECHANISM Original Filed May 10, 1962ZSheetS Shee tj INVENTOR. Moscow K ark nova United States Patent 26,862ROTARY SPEED-CHANGE-SENSING MECHANISM Moscow K. Richmond, 2819 ButlerAve., Los Angeles, Calif. 90064 Original No. 3,233,162, dated Feb. 1,1966, Ser. No. 193,733, May 10, 1962. Application for reissue Jan. 26,1968, Ser. No. 706,996

Int. Cl. H02p 5/00 US. Cl. 318264 18 Claims Matter enclosed in heavybrackets [II appears in the original patent but forms no part of thisreissue specification; matter printed in italics indicates the additionsmade by reissue.

ABSTRACT OF THE DISCLOSURE The invention provides a speed-ehange-sensingmechanism equipped with first arid second independently rotatablemembers which are adapted to be driven in rotation in unison. The rotaryspeed of the first member provides a reference speed, while the rotaryspeed of the second member is ddapted to be changed independently of therotary speed of the first member.

This invention relates generally to a mechanism for sensing changes inthe speed of a moving member and, particularly, to a rotaryspeed-change-sensing mechanism for sensing changes in the rotary speedof a rotating member.

Stated briefly, the invention provides a speed-changesensing mechanismequipped with first and second independently rotatable members which areadapted to be normally driven in rotation in unison. The rotary speed ofthe first member provides a reference speed, while the rotary speed ofthe second member is adapted to be changed independently of the rotaryspeed of the first member.

Operatively connected with these members, respectively, are first andsecond movable fulcrums which rockably support an arm engaged by athird, stationary fulcrum and which are moved in unison, by rotation ofsaid members in unison, in such a way as to rock said arm on itsstationary fulcrum. If the relative rotary speed of the second memberwith respect to the first member is reduced, continued movement of thefirst fulcrum, operatively connected with the first member, rocks thelever on the second fulcrum out of engagement with the stationaryfulcrum.

In the illustrative embodiments of the invention, the first fulcrum isdriven in gyration by rotation of the first member. The second fulcrumis drivably connected by a sirp coupling, such as a friction clutch, tothe second member in su'ch manner that rotation of the latter memi herin one direction exerts a force on the second fulcrum tending to rockthe arm about the gyratory fulcrum and into engagement with thestationary fulcrum. During normal operation of the mechanism, then, withsaid members turning in unison, the force exerted on the second fulcrumyieldably retains the arm in contact with the stationary fulcrum so thatthe arm is rocked on the latter fulcrum by the gyratory motion of thegyratory fulcrum. During one-half of each gyration of the latterfulcrum, the second fulcrum is moved in one direction by the forceexerted thereon by the rotating second chamber, while during the otherhalf of each gyration of the gyratory fulcrum, the second fulcrum ismoved in the opposite direction and against the latter force exertedthereon so that slippage occurs in the slip coupling between the secondmember and the second fulcrum.

Re. 26,862 Reissued Apr. 21, 1970 ice From this discussion, it isobvious that during normal operation of the mechanism, the secondfulcrum is oscillated in unison with gyration of the gyratory fulcrum,the oscillatory fulcrum being moved in one direction of its oscillationunder the action of the force exerted on the latter fulcrum by therotating second member and in the opposite direction of its oscillationunder the action of the force exerted on the arm by the gyratoryfulcrum.

Assume now that rotation of the second rotary member of the presentmechanism is arrested just as the oscillatory fulcrum commences its halfcycle of movement in the direction of the force exerted on the fulcrumby rotation of the second member or at some other point in this halfcycle, while rotation of the first rotary member, and, hence, gyrationof the gyratory fulcrum, is continued, Under these conditions, theoscillatory fulcrum becomes a stationary fulcrum on which the arm isrocked out of engagement with the first-mentioned stationary fulcrum bycontinued gyration of the gyratory fulcrum. If the rotary motion of thesecond rotary member is arrested during the other half cycle of movementof the oscillatory fulcrum, the motion of the gyratory fulcrum continuesthe movement of the oscillatory fu'lcrum to the end of the half cycleand then rocks the arm on the latter fulcrum out of engagement with thestationary fulcrum. Essentially the same actions as those describedabove will, of course, occur if the second rotary member is merelyslowed rather than completely arrested.

In the present rotary speed-change-sensing mechanism, then, rocking ofthe arm out of engagement with the stationary fulcrum signals areduction in the relative rotary speed of the second rotary member withrespect to the first rotary member. An added feature of the illustrativeembodiments of the invention resides in the provision of a secondstationary fulcrum to permit either direction of rotation of the rotarymembers.

A typical application of the present rotary speed-changesensingmechanism is sensing overloads in a mechanical power transmissionsystem. In this case, the second rotary member of the mechanismcomprises a rotary power transmission member to be operatively connectedin the power transmission system in such a way that it is slowed orarrested by an overload in the system. The rocking motion of the arm ofthe speed-change-sensing mechanism which occurs in repsonse to thisslowing or arresting of the power transmission member can be utilized toeffect a desired control function in the power transmission system.

In one illustrative form of the invention, for example, the arm actuatesan electrical switch for deenergizing a reversible motor for driving thepower transmission system and conditioning the motor for reverserotation. In another illustrative form of the invention, the armactivates a control device for an internal combustion engine whichdrives the power transmission system in which the rotary powertransmission member of the mechanism is connected. In a thirdillustrative form of the invention, the arm controls a rotarytransmissioin. It will become evident as the description proceeds thatthe above represent only a few of the many different applications andmodes of operation of the present mechanism.

The illustrative embodiments of the invention possess various featuresof construction and operation in addition to those mentioned above, suchas a manual reset feature and a limit stop feature, which will becomereadily evident as the description proceeds.

In view of What has been said heretofore, it is evident that a generalobject of the invention is to provide a new and unique rotaryspeed-change-sensing mechanism for sensing changes in the rotary speedof a member.

Another object of the invention is to provide a mechanism of thecharacter described which can be designed to perform any desired controlfunctions in response to speed changes sensed by the mechanism.

Yet another object of the invention is to provide a rotaryspeed-change-sensing mechanism which can be utilized to sense overloadsin power transmission systems.

A further object of the invention is to provide a mechanism of thecharacter described for use in a mechanical power transmission systemand having a unique limit stop feature for controlling the system inresponse to predetermined movement of a driven member of the system.

Yet a further object of the invention is to provide a mechanism of thecharacter described which is relatively simple in construction,economical to manufacture, immune to malfunctioning, and otherwiseideally suited to its intended purposes.

Other objects, advantages, and features of the invention will becomeevident as the description proceeds Certain illustrative embodiments ofthe present invention will now be described in detail by reference tothe attached drawings, wherein:

FIG. 1 is a side elevation of a portion of a mechanical powertransmission system embodying one form of the present rotaryspeed-change-sensing mechanism;

FIG. 2 is an enlarged section taken along line 2-2 in FIG. 1 andillustrating the rotary speed-changesensing mechanism embodied in thepower transmission system of FIG. 1;

FIG. 3 is a side elevation of the mechanism in FIG. 2 illustrating theparts thereof in one position of operation;

FIG. 4 is a section taken along line 44 in FIG. 3;

FIG. 5 is a view similar to FIG. 3 showing the parts of the mechanism inanother position of operation;

FIG. 6 is a view similar to FIGS. 3 and 5 illustrating the parts of themechanism in yet another position of operation;

FIG. 7 is a side elevation of the rotary speed-changesensing mechanismillustrated in FIGS. 1 and 2, on reduced scale, and showing a controlcircuit to be operated by the mechanism;

FIG. 8 is a side elevation of a modified form of the present rotaryspeed-change-sensing mechanism;

FIG. 9 is a side elevation of a further modified form of the presentrotary speed-change-sensing mechanism;

FIG. 10 is a side elevation of yet a further modified form of thepresent rotary speed-change-sensing mechanism; and

FIG. 11 illustrates an alternative electrical switching circuit for usewith the present speed-change-sensing mechanism in place of theswitching circuit of FIG. 7.

In FIGS. 1-7, the present rotary speed-change mechanism is designated bynumeral 20. This mechanism includes a central shaft 22 driven inrotation from a reversible motor 24 through a speed reduction unit 26.Fixed to the shaft 22, as by a pin 28, is a first rotary member or disc30. Rotatable on the shaft 22, next to the member 30, is a second rotarydisc or power transmission member 32. Member 32 has been illustrated ascomprising a grooved pulley, around which is trained a belt 34.Obviously a cable, chain, or other similar drive could be used in placeof the illustrated belt drive. Fixed to one of the members 30 or 32, saymember 30, is a disc 36 of friction material which, as will be seen,forms a slip or friction coupling between the members 30 and 32.

Power transmission member 32 includes an integral hub 38 on which isrotatable a third disc or rotary member 40. Disposed between and fixedto one of the members 30 or 40, say member 40, is a disc 42 of frictionmaterial. Threaded on the hub 38 of the member 32 is a nut 43. Conicalsprings 44 are mounted on the hub 38 between the member 40 and the nut43. Springs 44, therefore, resiliently urge the member 40 toward thepower transmission member 32 and, thereby, urge the friction disc 42secured to the member 40 into frictional contact with the adjacent sideface of the power transmission member 32. From this discussion, it isclear that the friction disc 42 forms a slip coupling between themembers 32 and 40, whereby the member 40 is adapted to be driven inrotation by the member 32 and to slip with respect to the latter member.

Slidable on the shaft 22, outboard of the hub 38 of the powertransmission member 32, is a gyratory fulcrum or eccentric 46. Fulcrum46 is keyed against rotation on the shaft 22 by means of a pin 48 on thefulcrum engaging in a slot 50 in the shaft 22.

The outer end of shaft 22 is threaded to receive a nut 52. Mounted onthe shaft 22, between the fulcrum 46 and the nut 52, is a multiplicityof spring washers 54. These spring washers urge the fulcrum 46 againstthe hub 38 of the power transmission member 32 and, thereby, the lattermember against the friction disc 36 secured to the member 30. From thisdescription, it is evident that the friction disc 36 provides a slip orfriction coupling be tween the member 30 and the power transmissionmember 32, whereby the latter member is adapted to be driven in rotationby the member 30, and, therefore, the shaft 22, and to slip with respectto the member 30 and the shaft 22.

Carried on the member 40 is a shoulder screw 56 which functions as, andwill hereinafter be referred to as, an oscillatory fulcrum. Rockablysupported on the fulcrums 46 and 56 is an arm 58. Thus, arm 58 has abore 60 which receives the shoulder of the screw or oscillatory fulcrum56 with a close, but rotatable fit so that the arm 58 is pivotally orrockably supported on the member 40 by the fulcrum 56. Also, the arm 58has a rectangular opening or slot 62 to receive the eccentric orgyratory fulcrum 46. This latter fulcrum has a peripheral groove 64 inwhich the upper and lower edges of the arm opening 62 engage. Thespacing between the upper and lower edges of the opening 62 in the armis approximately the same as the diameter of the bottom of the fulcrumgroove 64 while the larger dimension of the arm opening is somewhatgreater than this diameter.

From the preceding description, it is evident that if the oscillatoryfulcrum 56 is stationary, rotation or gyratory motion of the eccentricor gyratory fulcrum 46 rocks the arm 58 on the fulcrum 56. Similarly,the force or torque exerted on the member 40, through the slip coupling42, during rotation of the power transmission member 32 tends to rockthe arm 58 on the gyratory fulcrum 46 in one direction or the otherdepending upon the direction of rotation of the member 32.

Stationarily mounted at the left-hand end of the arm 58, as themechanism is viewed in the drawings, is an upstanding bracket 66 havingan integral element 68 thereof bent into parallelism with the arm 58.The left-hand end of the arm is bent at right angles and formed with aslot 70, the upper and lower edges 72 and 74 of which straddle thebracket element 68. It will be observed that if the left-hand end of thearm 58 is rocked downwardly about the gyratory fulcrum 46, as the arm isviewed in FIGS. 1 and 4, the upper edge 72 of the slot 70 in the armengages the upper edge 76 of the bracket element 68. Similarly, if theleft-hand end of the arm 58 is rocked upwardly, the lower edge 74 of theslot 70 in the arm engages the lower edge 78 of the bracket element 68.

Now assume that the motor 24 is energized to drive the shaft 22 in theclockwise direction as it is viewed in FIG. I. Clockwise rotation of theshaft 22 drives the power transmission member 32 in the clockwisedirection, by virtue of the slip or friction coupling 36 between thismember and the member 30 fixed to the shaft. Clockwise rotation of thepower transmission member 32, in turn, transmits a clockwise torque tothe member 40, and the oscillatory fulcrum 56 carried thereon, by virtueof the slip or friction coupling 42 between the latter members. Thisclockwise torque or force on the oscillatory fulcrum 56 rocks the arm 58on the gyratory fulcrum 46 in the clockwise direction until the loweredge 74 of the slot 70 in the arm engages the lower edge 78 of thebracket element 68. The gyratory fulcrum 46, of course, is rotated orgyrated by rotation of the shaft 22. It will be evident that duringone-half of each revolution or gyration of the fulcrum 46, theright-hand end of the arm 58 and, therefore, the oscillatory fulcrum 56are permitted to descend (FIG. 3) under the action of the force ortorque exerted on the fulcrum 56 by the slip coupling 42 between themembers 32 and 40. The downward force on the fulcrum 56, of course,constantly urges the arm 58 in the clockwise direction on the gyratoryfulcrum 46 to maintain the lower edge 74 of the arm slot 70 in contactwith the lower edge 78 of the bracket element 68 during downwardmovement of the right-hand end of the arm 58 and the fulcrum 56.Accordingly, the arm 58 rocks on the lower edge 78 of the bracketelement 68 and about the edge 74 of the arm during this downwardmovement of the fulcrum 56 and the right-hand end of the arm 58. Duringthe remaining half of each revolution or gyration of the gyratoryfulcrum 46, the latter elevates (FIG. 5) the righthand end of the arms58 and the oscillatory fulcrum 56. During this upward movement of thefulcrum 56, the member 32 continues to be driven in the clockwisedirection of rotation by the shaft 22 so that the slip coupling 42between the members 32 and 40 slips. In other words, during upwardmovement of the right-hand end of the arm 58 and the fulcrum 56, by themotion of the gyratory fulcrum 46, the member 40 slips with respect tothe member 32 and is rotated with respect to the latter member in adirection opposing the direction of rotation of the latter member.During the upward motion of the right-hand end of the arm 53 and thefulcrum 56, of course, the torque transmitted from the clockwiserotating member 32 to the member 40 continues to exert a downward forceon the fulcrum 56 Which maintains the lower edge 74 of the arm slot 70in contact with the lower edge 78 of the bracket element 68.Accordingly, here, again, the arm 58 is rocked on the lower edge 78 ofthe bracket element 68 and about the edge 74 of the arm.

It is evident, therefore, that during clockwise rotation of the shaft22, the arm 58 is caused to rock on the lower edge 78 of the bracketelement 68 by the combined action of the gyration of the gyratoryfulcrum 46 and the continuous downward force which is exerted on theoscillatory fulcrum 56. The lower edge 78 of the bracket element 68,therefore, provides a stationary fulcrum for the arm 58. It is alsoclear that during the above-described rocking of the arm 58 on thestationary fulcrum 78, the fulcrum 56 is oscillated up and down aboutthe axis of the shaft 22, the latter fulcrum being moved in onedirection of its oscillation by the torque or force transmitted from therotating member 32 to the member 40 and in the opposite direction of itsoscillation by the force transmitted from the gyratory fulcrum 46through the arm 58 to the fulcrum 56.

If the shaft 22 is rotated in the opposite direction, i.e., thecounterclockwise direction as it is viewed in FIG. 1, the left-hand endof the arm is rocked downwardly, by the then upward force on the fulcrum56, until the upper edge 72 of the arm slot 70 engages the upper edge 76of the bracket element 68. The arm is caused to rock on this upper edgeof the bracket element by the combined action of the gyration of thegyratory fulcrum 46 and the continuous upward force on the oscillatoryfulcrum 56. As before, the latter fulcrum is simultaneously oscillated.In this case, then, the upper edge 76 of the bracket element 68 providesa stationary fulcrum for the arm 58 on which the latter is rocked duringcounterclockwise rotation of the shaft 22.

Assume now that as the shaft 22 is being driven in either direction ofrotation by its motor 24, say in the clockwise direction, the member 32is suddenly restrained against rotation with the shaft just as thefulcrum 56 commences its downward movement or at some point in thisdownward movement. When this occurs, the member 30 continues to rotatewith the shaft and slippage occurs in the slip coupling 36 between themember 30 and the member 32. With the member 32 thus arrested, thedownward bias force normally exerted on the oscillatory fulcrum 56during rotation of the member 32 with the shaft 22 ceases. The slipcoupling 42 between the now stationary member 32 and the member 40resists relative rotation of members 32 and 40 and, therefore, movementof the fulcrum 56 in either direction of its oscillation. The gyratoryfulcrum 46, of course, continues to be driven in gyration by thecontinuously rotating shaft 22. It is evident that continued gyration ofthe gyratory fulcrum 46 with the downward bias force on the oscillatoryfulcrum 56 thus removed and with downward movement of the latter fulcrumthus resisted rocks the arm 58 on the oscillatory fulcrum 56 (FIG. 6) ina direction to move the left-hand end of the arm downwardly out ofengagement with the stationary fulcrum 78 engaged by the arm duringnormal clockwise rotation of the member 32 with the shaft 22. Sufficientrocking of the arm 58 in this direction on the oscillatory fulcrum 56,of course, will result in engagement of the arm with the upperstationary fulcrum 76.

Assume now that the member 32 is arrested during clockwise rotationthereof and just as the oscillatory fulcrum 56 commences its upwardmovement or at some point in this upward movement of the latter fulcrum.As just noted, when the member 32 is held stationary, the slip coupling42 resists upward movement of the fulcrum 56. This resistance to upwardmovement of the fulcrum 56 creates a downward force on the latterfulcrum during continued gyration of the fulcrum 46 which retains thearm 58 in contact with the lower stationary fulcrum 78. As a result,gyration of the gyratory fulcrum 46 continues to rock the arm on thelower stationary fulcrum 78 and move the fulcrum 56 upwardly until thelatter reaches the upper limit of its oscillation. Fulcrum 56 thenremains stationary at this upper limit. Continued gyration of fulcrum 46rocks the arm 58 on the now stationary oscillatory fulcrum out ofengagement with the lower stationary fulcrum 78 in precisely the sameway as just described.

If the member 32 is arrested when the shaft 22 is being driven in thecounterclockwise direction, essentially the same actions occur in themechanism as those described above except that the various movementswhich take place in the mechanism when the member 32 is arrested occurin one direction when the shaft 22 rotates in the clockwise directionand in the opposite direction when the shaft 22 rotates in thecounterclockwise direction. Thus, if the member 32 is arrested duringcounterclockwise rotation of the shaft 22, the arm 58 is rocked on thestationary oscillatory fulcrum 56 out of engagement with the upperstationary fulcrum 76, engaged by the arm during normal counterclockwiserotation of the member 32, and into engagement with the lower stationaryfulcrum 78.

From the preceding discussion, it is evident that when the shaft 22 isdriven in either direction of rotation by its motor 24 and the member 32is free to rotate with the shaft, the arm 58 is rocked on either theupper stationary fulcrum or the lower stationary fulcrum 78, dependingupon the direction of rotation of the shaft, and the oscillatory fulcrum56 is oscillated up and down. If the member 32 is suddenly restrainedagainst rotation with the shaft 22 rotating in either direction, the arm58 is rocked on the then stationary oscillatory fulcrum 56 out ofengagement with its currently engaged stationary fulcrum 76 or 78, asthe case may be, and into engagement with the other stationary fulcrum.Arresting of the member 32 while the oscillatory fulcrum 56 is moving inthe direction of rotation of the shaft 22 results in immediate rockingof the arm 58 in the manner described. On the other hand, arresting ofthe member 32 while the oscillatory fulcrum 56 is being moved in adirection opposite to the direction of rotation of the shaft 22 resultsin continued movement of the oscillatory fulcrum to the limit of itsoscillation in this direction and then in rocking of the arm 58 in themanner described.

In the foregoing discussion, it has been assumed that the rotary motionof the member 32 is completely arrested. It is obvious, however, thatessentially the same actions will occur in the rotaryspeedchange-sensing mechanism if the rotaly speed of the member 32 ismerely reduced. In this case, of course, the oscillatory fulcrum 56 willcontinue to move at a reduced rate of speed. Continued gyration of thegyratory fulcrum 46 at its normal speed of gyration, however, will causerocking of the arm 58 on the slowly moving oscillatory fulcrum 56 inesentially the same way as described above where the rotary movement ofthe member 32 is completely arrested. If the rotary speed of the member32 is reduced while the oscillatory fulcrum 56 is moving in thedirection of rotation of the shaft 22, of course, the latter fulcrumwill continue to be moved at its normal speed to the limit of itsmovement in this direction, whereupon it commences movement in theopposite direction at a reduced speed and the arm 58 is rocked on theslowly moving oscillatory fulcrum by gyration of the gyratory fulcrum46.

From the discussion thus far, it is evident that rocking of the arm 58on one or the other of the stationary fulcrums 76 or 78, depending uponthe direction of rotation of the shaft 22, signals or indicates that themember 32 is rotating in unison with the shaft 22 and at the same speedas the shaft. Rocking of the arm 58 on the oscillatory fulcrum 56 out ofengagement with one of the stationary fulcrums 76 or 78 and intoengagement with the other stationary fulcrum signals or indicates areduction in the rotary speed of or complete arresting of the member 32.Clearly, then the mechanism described above is adapted to sense a changein the rotary speed of the member 32. In the described mechanism, thegyratory speed of the gyratory fulcrum 46 actually serves as a referencespeed and the mechanism senses a deviation of the relative speed of themember 32 with respect to the gyratory speed of the fulcrum 46 from apredetermined normal relative speed. Thus, if the motor 24 isalternately started and stopped, the rotary speed of the shaft 22, and,therefore, the reference gyratory speed of the gyratory fulcrum 46,changes. The rotary speedchange mechanism, however, will continue tofunction normally so long as the member 32 continues to rotate in unisonwith gyration of the gyratory fulcrum, or, in other words, so long asthe relative rotary speed of the member 32 with respect to the gyratoryspeed of the fulcrum 46 remains constant. It is, therefore, the relativespeed of the member 32 and the fulcrum 46, and not the absolute speed ofthese parts, which controls the operation of the mechanism.

In a typical application of the rotary speed-changesensing mechanismdescribed above, the belt 34 is trained about a second pulley (notshown) in a power transmission system so that the torque for driving thesystem is transmitted through the rotary power transmission member 32 ofthe mechanism 20. The tension of the springs 54 of the mechanism is soadjusted, by positioning of the nut 52, that the torque required tocause slippage of the slip coupling 36 between the members and 32 and,thereby, relative rotation of these members is slightly greater than thetorque which is required to be transmitted from the member 30 to themember 32 to drive the power transmission system during normal load ingthereof. When the load on the power transmission system is normal, orless than normal, therefore, the rotary power transmission member 32 ofthe present mechanism 20 is driven in unison with the gyratory fulcrum46. Under these conditions, arm 58 of the mechanism 20 is rocked on oneor the other of the stationary fulcrums 76 or 78, depending upon thedirection of rota tion of the shaft 22 of the mechanism. In the event ofan overload in the power transmission system that requires a greaterinput torque than the slip coupling 36 can transmit without slippage,the rotary power transmission member 32 of the mechanism 20 isrestrained against rotation in unison with the gyratory motion of thegyratory fulcrum 46. Under these conditions, the arm 58 of the mechanismis rocked on the oscillatory fulcrum 56 out of engagement with thestationary fulcrum 76 or 78 previously engaged by the arm.

This rocking of the arm 58 which occurs in response to an overload inthe power transmission system and the attendant change in the relativerotary speed of the rotary power transmission member 32 with respect tothe gyratory speed of the gyratory fulcrum 46 can be used to perform anydesired control function. In the drawings, for example, this rocking ofthe arm is utilized to deenergize the motor 24 for driving the mechanism20 and the power transmission system.

To this end, there is mounted on the upstanding bracket 66 an electricaltoggle switch 80, the toggle arm 82 of which extends through a reducedcontinuation 84 of the slot 70 in the bent left-hand end of the arm 58.The slots 70 and 84, and the width of stationary fulcrum forming element68 of the bracket 66, are so proportioned that the switch arm 82 isoperated to one position by movement of the left-hand end of the arm 58between its upper position in which it engages the lower stationaryfulcrum 78 and its lower position in which the arm engages the upperstationary fulcrum 76. Similarly, the switch arm 82 is operated to itsother position by movement of the left-hand end of the arm 58 betweenits lower position of engagement with the upper stationary fulcrum 76and its upper position of engagement with the lower stationary fulcrum78. Thus, during normal operation of the power transmission system withthe shaft 22 turning in either direction of rotation, the arm 58 of themechanism 20 rocks about one or the other of the stationary fulcrums 76or 78 and the switch arm 82 remains in the corresponding position. Whenan overload occurs in the system, the arm 58 is rocked into engagementwith the other stationary fulcrum, thereby operating the switch arm 82from one position to the other. This operation of the switch 80, forexample, could serve merely to deenergize the motor 24 and thereby stopoperation of the power transmission system. In the drawings, however,switch is shown in FIG. 7 to be a double pole, double throw switch, theterminals of which are connected to the stator winding 24S and the rotorwinding 24R of the motor 24 in the manner illustrated in FIG. 7. Twoother terminals of the switch 80 are connected to two terminals 86A, 86Bof latching relay 86, the blade terminal 86E of which is connected toone terminal 88 of an electrical power source 90. The remaining terminalof the switch 80 is connected to the other terminal 92 of the powersource 90. The coil 86C of the relay 86 is connected to an electricalpower source 94 through a push button 96. The latching relay 86 is aconventional latching relay having a movable blade or contact 86D whichis alternately moved into and locked in engagement with the relaycontacts 86A and 86B in response to successive energizing of the relaycoil 86C. Thus, assuming that the relay contact 86D initially engagesthe relay contact 86A, the first closure of the push button 96 shiftsthe relay contact 86D to the other relay contact 86B. The followingclosure of the push button 96 returns the relay contact 86D tothe relaycontact 86A.

The motor 24 is energized to drive the rotary speedchangesensingmechanism 20 and the power transmission system operated thereby bydepressing the push button 96 to shift the relay contact 86D to thatrelay contact 86A or 86B which is currently connected in circuit withthe motor stator and rotor windings 24S and 24R by the switch 80. In theillustrated condition of the switch 80, for example, relay contact 86Ais connected in circuit with the motor windings. Operation of the pushbutton 96 to shift the relay contact 86D to the relay contact 86A, then,energizes the motor 24 to drive the mechanism 20 and the powertransmission system operated thereby. So long as the load on the systemis normal or below normal, the arm 58 of the mechanism 20 will continueto rock about the respective stationary fulcrum 76 or 78 and the switcharm 82 will remain in its current position. If an overload occurs in thepower transmission system, the switch arm 82 is tripped by the arm 58 ofthe mechanism 20, in the manner described earlier. Tripping of theswitch arm 82 operates the switch 80 to reverse the switch connectionsof the stator 245 of the motor 24 and place the motor windings 24S and24R in circuit with the currently open relay contact 863. The motor isthereby deenergized and conditioned for rotation in the reversedirection upon subsequent closure of the push button 96. When the pushbutton is again operated, the relay contact 86D is shifted to relaycontact 86B to energize the motor 24 in the reverse direction. Thisarrangement is particularly useful in power transmission systems inwhich the latter must be backed off following an overload before thelatter can be removed. The arrangement described above is suitable, forexample, for a garage door operator in which overloads generally occuras a result of the door encountering an obstruction either while it isbeing closed or opened. In this latter application, it is evident thatthe present rotary speedchange-sensing mechanism 20 is capable ofserving both as a limit switching device for shutting off the garagedoor operating motor in response to the door engaging stops in its fullyopened and fully closed positions and as a safety switch for shuttingoff the garage door operating motor in the event the door encounters andobstruction, such as a person standing in the path of movement of thedoor.

It is evident that the rocking motion of the arm 58 of the presentrotary speed-change-sensing mechanism 20 which occurs in response to anoverload in the power transmission system operated by the mechanism canbe utilized to perform control functions other than that describedabove. For example, the mechanism 20 can be used to drive an electricalgenerator for energizing a variable electrical load which may overloadthe generator, thereby creating a mechanical overload in the systemwhich rocks the arm on the rotary speed-change-sensing mechanism in themanner described. In this case, the arm may operate a suitableelectrical control device for reducing the load on the generator. Inthis respect, it Will be noted that the shaft 22 and the gyratoryfulcrum 46 of the mechanism 20 can continue to rotate even though thepower transmission member 32 is restrained against rotation with thegyratory fulcrum. In this case, of course, the arm 58 of the mechanismwill be oscillated back and forth between the stationary fulcrums 76 and78 and the oscillatory fulcrum 56 of the mechanism will be oscillatedback and forth between its limits of oscillation. As a result, if thegyration of the gyratory fulcrum of the mechanism is continued while therotary power transmission mechanism 32 of the mechanism is restrainedagainst rotation, as it is during an overload in the power transmissionsystem which it drives, any control device operated by the arm wouldcontinue to be actuated back and forth between its two positions. Thiswould necessitate a specially designed control device in thoseapplications of the mechanism in which the arm of the mechanism operatesto control the load on the power transmission system in some way withoutdiscontinuing the gyratory motion of the gyratory fulcrum 46. It is alsoapparent, however, that when the overload is removed, so that the rotarypower transmission member 32 again rotates in unison with the gyratoryfulcrum 46, normal operation of the mechanism is resumed.

In the drawings, the member 32 and the gyratory fulcrum 46 are bothdriven from the same power source.

It is conceivable, however, that the member 32 may be driven by onepower source and the gyratory fulcrum 46 by another power source inwhich case the rotary speedchange-sensing mechanism 20 of this inventionmay be used to sense changes in the relative speed of the one powersource with respect to the other power source. The rocking motion of thearm 58 of the mechanism which would then occur in response to areduction in the speed of the one power source with respect to the otherpower source could be utilized to actuate a control device forincreasing the relative speed of the one power source to normal. In thissituation, then, the present rotary speed-change-sensing mechanism wouldserve as a means for synchronizing the operation of the two powersources. As shown in FIG. 7, a limit stop 97 may be attached to the belt34 and the arm 58 of the rotary speed-changesensing mechanism 20 may beprovided with an inclined camming surface 98 to be engaged by this stopfor rocking the arm 58 on the oscillatory fulcrum 46 of the mechanism,and thereby operating the switch arm 82, after predetermined travel ofthe belt. Thus, it will be observed in FIG. 7 that when the limit stop97 engages the inclined surface 98 on the arm 58, the right-hand end ofthe latter is cammed upwardly to rock the arm about the oscillatoryfulcrum 46 in a direction to actuate the switch arm 82. The arm 58 mayhave a second inclined surface 100 for engagement by the limit stop 97,or an additional limit stop on the belt 34, during operation of themechanism in the reverse direction. The extended right-hand end of thearm 58 is also adapted to be grasped for manual operation of the switchby manual rocking of the arm 58 on the oscillatory fulcrum 46. In thisconnection, it will be observed that if the right-hand end of the arm 58is sufficiently laterally extended, the abovedescribed limit stopactions will occur whether the righthand end of the arm is being rockedup or down as the limit stop 97 approaches the arm.

In the rotary speed-changesensing mechanism 20 described above, it isapparent that during normal operation, the arm 58 of the mechanismfunctions as a lever which is fulcrumed at one end (stationary fulcrum76 or 78), which has a load applied to its other end (bias force on theoscillatory fulcrum S6), and which is moved by a force applied betweenits ends (gyratory fulcrum 46). This will be immediately recognized asthe action of a third class lever. During an overload, the arm 58 againforms a lever which is fulcrumed at one end (oscillatory fulcrum 56),which has a load applied to its other end (the resistance of the switcharm 82), and which is moved by a force applied between its ends(gyratory fulcrum 46). Here, again, the arm 58 acts as a third classlever.

FIG. 8 illustrates a modified rotary speed-change mechanism 20Aaccording to the invention. Mechanism 20A is identical to the earliermechanism 20 except the oscillatory fulcrum 56 of the mechanism 20A islocated between the gyratory fulcrum 46 and the stationary fulcrums 76,78. Mechanism 20A also operates in substantially the same way asmechanism 20. Thus, during normal operation of mechanism 20A, i.e.,during rotation of the rotary power transmission member 32 with shaft22, arm 58A is rocked on one or the other of the stationary fulcrums 76or 78, depending on the direction of rotation of the member 32, by thecombined action of the gyratory motion of the gyratory fulcrum 46 andthe bias force exerted on the oscillatory fulcrum 56 by virtue of theslip coupling (not shown in FIG. 8) between members 32 and 40. It isobvious that during such normal operation of mechanism 20A, arm 58A actsas a second class lever.

If member 32 is arrested, continued gyration of the gyratory fulcrum 46rocks the arm 58A on the then stationary oscillatory fulcrum 56 andtrips the switch 80, as before. In this case, the arm obviously acts asa first class lever. In the earlier mechanism 20, then, its arm 58 actsas a third class lever both during normal operation of the mechanism andwhen its rotary power transmission member 32 is arrested. In mechanism20A, on the other hand, its arm 58A acts as a second class lever duringnormal operation of the mechanism and as a first class lever when therotary power transmission member 32 of the latter mechanism is arrested.

In FIGS. 18, the shaft 22 of the present rotary speedchange-sensingmechanism actuates a switch and is directly coupled to the power source,or motor, for the power transmission system in which the mechanism isused. In this case, then, the mechanism is situated at the power inputend of the system. In some cases, it may be desirable or necessary tohave the mechanism actuate some other control device than a switchand/or to have the mechanism situated at some intermediate position inthe system. FIG. 9 illustrates such an arrangement.

In this figure, the shaft 22 of the mechanism 20B, which is like themechanism 20A of FIG. 8 except for the differences hereinafter noted,has a gear 200 keyed thereon. This gear is driven in rotation, to drivethe mechanism 20B, through a gear train 202. In FIG. 9, the rotary powertransmission member 32B of the mechanism comprises a gear, instead of apulley as in FIGS. l-S. Gear 328 drives a second gear train 204. Geartrains 202 and 204, then, comprise a power transmission system havingthe present rotary speed-change-sensing mechanism 208 connected at anintermediate position therein.

The arm 58B of the mechanism 20B is somewhat longer than the arm in themechanisms of FIGS. l8 and rotatably mounts a gear 206 of the gear train202. Gear 206 I is adapted to normally mesh with, and thereby drivablycouple, two other gears 208 and 210 of the gear train 202. Gear 210meshes with gear 200 on the shaft 22 of the mechanism 20B. Gear train202 is driven from a power source (not shown) in such a way that theshaft 22 and, 3

rotary speed-change-sensing mechanism 20B. The shaft I 212 of the gear206 forms a stationary fulcrum for the arm 58B about which the latter isrocked, by gyration of the gyratory fulcrum 46, during normal operationof the mechanism. The hole 60B in the arm 583 through which theoscillatory fulcrum 56 extends is elongated in the mechanism underconsideration so that the oscillatory motion imparted to the fulcrum 56,about the axis of the shaft 22, during gyration of the fulcrum 46, doesnot tend to move the gear 206 back and forth.

When the portion of the power transmission system to the right of themechanism 203, i.e., gear train 204, is operating under normal load, thegear 206 is maintained in meshing engagement with the gears 208 and 210,whereby the gear train 204 is driven through the mechanism 208, as justindicated. During this normal operation of the system, the arm 58B isrocked on the stationary fulcrum, or gear shaft 212. In the event of anoverload in the gear train 204, or in a following portion of the powertransmission system driven by the latter gear train, the gear 32B of themechanism is slowed or completely arrested. The shaft 22, and,therefore, the gyratory fulcrum 46 of the mechanism, however, continuesto be driven through the gear train 202. Continued gyration of thefulcrum 46 rocks the arm 58B on the oscillatory fulcrum 56, as in theprevious forms of the in vention, in a direction which disengages thegear 206 on the arm from the gears 208 and 210. The mechanism 208 andthe gear train 204 then cease to be driven from the gear train 202. Thepower transmission system can be restarted, after removal of theoverload, by manually rocking the arm 58B of the then stationarygyratory fulcrum 46 to re-engage the gear 206 on the arm with the gears208 and 210.

In FIG. 10, the shaft 22 of the illustrated rotary speedchange-sensingmechanism 20C is driven from an internal combustion engine 300. In thiscase, the stationary fulcrum for the arm 58C of the mechanism isfurnished by an arm 302 on the rotatable valve member 304 of a fuelshut-off valve 306 for the engine 300. The valve arm 302 engages in aslot 308 in the arm 58C of the mechanism. In this case, the shaft 22and, therefore, the pulley 32 of the mechanism are driven in theclockwise direction indicated so that the left-hand end of the arm SSCis urged upwardly by the normally downward force on the oscillatoryfulcrum S6 of the mechanism. Shut-off valve 306 for the engine 300includes a stop 310 for limiting upward swinging of the valve arm 302 tothe position illustrated.

From this description, it is evident that when the load on the powertransmission system driven by the mechanism 20C through belt 34 isoperating under normal load, the arm 58C is rocked on the valve arm 302which, therefore, serves as a stationary fulcrum for the arm. The valvearm 302 is retained in its upper limiting position of FIG. 10, in whichposition the valve 306 is open to pass fuel to the combustion chamber ofthe engine 300. In the event of an overload in the power transmissionsystem operated by the mechanism, the member or pulley 32 is slowed orcompletely arrested, as before. When this occurs, the left-hand end ofthe arm 58C is rocked downwardly, about the oscillatory fulcrum 56, bygyration of the gyratory fulcrum 46. The valve arm 302 is thereby swungdownwardly, which action closes the fuel shut-off valve 306 and stopsthe engine 300. A latch 311 retains the valve in its closed position toprevent it from being reopened by the inertia of the engine.

It will be immediately evident, of course, that the engine 300 may becontrolled, in response to rocking of the arm 58C, in other ways thanthat described above. The arm of the mechanism, for example, couldoperate a switch, in a manner similar to that described in connectionwith FIGS. l-S, for opening the ignition system of the engine. In thealternative, the drive shaft (not shown) of the engine 300 may bedrivably coupled to the shaft 22 of the rotary speed-change-sensingmechanism by a centrifugally actuated clutch (not shown), in which casethe arm of the mechanism could operate a throttle for slowing theengine, and thereby causing disengagement of the centrifugal clutch inresponse to an overload.

In FIG. 11, numeral 400 denotes a double pole double throw switch havingswitch blades 402 and 404. Connected between these blades is the fieldwinding 405 of the motor 24 which drives the speed-change-sensingmechanism 20 in FIG. 1. In this case, motor 24 is a series wound DC.motor. Switch blades 402 and 404 are mechanically connected to anactuator 406. This actuator engages in the slot 84 in arm 58 of thespeedchange-sensing mechanism 20 in a manner similar to the actuator 82of the switch in FIG. 7 so that the switch 400 is operated between itstwo closed positions by rocking of the arm.

In one closed position of switch 400, switch blades 402 and 404 engageswitch contacts 408 and 410, respectively. Contact 408 is connected toone fixed contact 412 of a conventional latching relay 414. The otherfixed contact 416 of this relay connects to one electrical power inputterminal 418 through an indicator light 420. The movable contact 422 ofthis relay is connected to the other power input terminal 424. The othercontact 410 of the double pole, double throw switch 400 is connected toone terminal of the rotor winding 426' of motor 24. The other terminalof this winding is connected to the input terminal 418.

Switch 400 has a second pair of contacts 428 and 430 which are engagedby the switch blades 402 and 404, re-

spectively, when the latter are shifted to their other closed position.Switch contact 428 is connected between the switch contact 410 and theadjacent end of the motor rotor winding 426, as shown. Switch contact430 is located between the latching relay contact 416 and the inputterminal 418, as shown.

In a lead 432 connected across the input terminals 418, 424 is theprimary of a transformer 434. The secondary of this transformer isconnected in series with the coil 436 of the latching relay 414 and anormally open push button switch 438. Latching relay 414 operates in thewell-known way to shift its movable contact 422 into engagement with thefixed relay contacts 412 and 416 a1- ternately in response to successiveenergizing of the relay coil 436. The relay coil can be energized, ofcourse, by momentarily closing the push button switch 438.

It is evident from the preceding description that if the motor 24 of thespeed-change-sensing mechanism 20 is driving in one direction inresponse to the double pole, double throw switch 400 occupying oneclosed position when an overload occurs, the latter switch is thrown toits other closed position by rocking of the arm 58 of thespeed-change-sensing mechanism 20 in the manner described earlier. If weassume, for example, that the blades 402, 404 of switch 400 and themovable contact 422 of relay 414 are in their solid line positions ofFIG. 11 when the overload occurs, the switch blades are thrown to theirdotted line positions. The connections to the field winding 405 arethereby reversed and the motor is deenergized. When the push buttonswitch 438 is closed to shift the movable relay contact 422 to itsdotted line closed position, the motor is restarted in the reversedirection. Thus, the electrical switching circuit just describeddeenergizes the drive motor of the overload sensing device in responseto an overload and simultaneously reconditions the motor for subsequentoperation in the reverse direction.

While in the illustrated forms of the invention, friction clutches areused, it is obvious other types of slip clutches may be employed, suchas magnetic clutches.

Clearly, then, various illustrative embodiments of the invention, fullycapable of attaining the several objects and advantages preliminarilyset forth, have been disclosed. These physical embodiments of theinvention are, of course, intended to be purely illustrative and notlimiting in nature, numerous modifications in the design, arrangement ofparts, and instrumentalities of the invention being possible within thespirit and scope of the following claims.

I claim:

1. In a rotary speed-change-sensing mechanism, the combination of:

a pair of rotary members,

an arm,

a stationary fulcrum engaging said arm,

a pair of independently movable fulcrums rockably supporting said armand movable in unison to rock said arm on said stationary fulcrum, and

means including slip coupling means associated with one of said fulcrumsfor drivingly connecting said fulcrums individually to said respectiverotary members,

the relative speed of movement of one of said movable fulcrums withrespect to the other movable fulcrum being adapted to be changed,whereby movement of one movable fulcrum rocks said arm on the othermovable fulcrum out of engagement with said stationary fulcrum.

2. In a rotary speed-change-sensing mechanism, the

combination of:

a pair of rotary members,

a first gyratory fulcrum,

a second ocsillatory fulcrum,

an arm rockably supported on said fulcrums,

means including slip coupling means associated with one of said fulcrumsfor drivingly connecting said fulcrums individually to said respectiverotary members,

a stationary fulcrum engaging said arm,

said first and second fulcrum being movable in unison to rock said armon said stationary fulcrum, and

the relative speed of movement of one of said first and second fulcrumswith respect to the other of the latter fulcrums being adapted to bechanged, whereby movement of one of said latter fulcrums rocks said armon the other of the latter fulcrums out of engagement with saidstationary fulcrum.

3. In a rotary speed-change-sensing mechanism, the

combination of:

a first [gratory] gyratory fulcrum,

a first rotary member drivingly connected to said first fulcrum,

a second [oscillator] oscillatory fulcrum,

a second rotary member,

means providing a slip coupling between said second rotary member andsaid second fulcrum for urging the latter in one direction of itsoscillation during rotation of said second rotary member in onedirection,

said slip coupling means being adapted to slip to permit movement ofsaid second fulcrum in the other direction of its oscillation,

an arm rockably supported on said fulcrums in such manner that the armis adapted to be rocked on said second fulcrum by gyration of said firstfulcrum and the force exerted on said second fulcrum by said secondrotary member during rotation of the latter in said one direction tendsto rock said arm in a given direction on said first fulcrum, and

a third fulcrum engaging said arm to limit rocking of the latter in saidgiven direction on said first fulcrum, whereby said arm is rocked onsaid third fulcrum and said second fulcrum is oscillated by gyration ofsaid first fulcrum and rotation of said second rotary member in said onedirection in unison, and said arm is rocked on said second fulcrum outof engagement with said third fulcrum by gyration of said first fulcrumduring a reduction in the relative rotary speed of said second rotarymember with respect to the gyratory speed of said first fulcrum.

[4. In a rotary speed-change-sensing mechanism, the

combination of:

a first rotary member,

a second rotary member,

means providing a slip coupling between said members, whereby saidsecond member is adapted to be driven in rotation by said first memberand to slip with respect to said first member,

a first gyratory fulcrum,

means for rotating said gyratory fulcrum at a speed independent of therotational speed of the first rotary member,

a second oscillatory fulcrum carried on said second member foroscillatory movement with the latter member about its axis of rotation,

an arm rockably supported on said fulcrums in such manner that said armis adapted to be rocked on said second fulcrum by gyration of said firstfulcrum and the torque exerted on said second member by said firstmember during rotation of the latter in one direction tends to rock saidarm in a given direction on said first fulcrum, and

a. third fulcrum engaging said arm to limit rocking of the latter insaid given direction on said first fulcrum, whereby said arm is rockedon said third fulcrum and said second fulcrum is oscillated by gyrationof said first fulcrum and rotation of said first member in said onedirection in unison, and said arm is rocked on said second fulcrum outof engagement with said third fulcrum by gyration of said first fulcrumduring a reduction in the relative rotary speed of said first memberwith respect to the gyratory speed of said first fulcrum] 5. In a rotaryspeed-change-sensing mechanism, the

combination of:

a rotary shaft,

2. first member rotatable on said shaft,

means providing a slip coupling between said shaft and member, wherebythe latter is adapted to be driven in rotation by said shaft and to slipwith respect to the shaft,

a second member rotatable on said shaft,

means providing a slip coupling between said members, whereby saidsecond member is adapted to be driven in rotation by said first memberand to slip with respect to said first member,

a first gyratory fulcrum fixed to said shaft to turn with the latter,

a second oscillatory fulcrum carried by said second member foroscillation with the latter member about said shaft,

an arm rockably supported on said fulcrums in such a way that said armis adapted to be rocked on said second fulcrum by gyration of said firstfulcrum and the torque exerted on said second member by said firstmember during rotation of the latter member in one direction with saidshaft tends to rock said arm in a given direction on said first fulcrum,and

a third fulcrum engaging said arm to limit rocking of the latter in saidgiven direction on said first fulcrum, whereby said arm is rocked onsaid third fulcrum and said second fulcrum is oscillated by rotation ofsaid first member in said one direction with the shaft, and said arm isrocked on said second fulcrum out of engagement with said third fulcrumby rotation of said shaft with said first member restrained againstrotation with the shaft.

6. In a rotary speed-change-sensing mechanism, the

combination of:

a rotary shaft,

a first disc fixed to said shaft,

a second disc rotatable on said shaft,

means for urging said discs into frictional contact,

whereby said second disc is adapted to be driven in rotation by saidfirst disc and to slip with respect to said first disc,

a third disc rotatable on said shaft,

means urging said third disc into frictional contact with said seconddisc, whereby said third disc is adapted to be driven in rotation bysaid second disc and to slip with respect to said second disc,

an arm pivoted on said third disc,

an eccentric fixed to said shaft and engaging in a slot in said arm,

the torque exerted on said third disc by said second disc duringrotation of the latter in one direction with said shaft tending to rocksaid arm in a given direction on said eccentric, and

means engaging said arm to limit rocking of the latter on saideccentric.

7. In a rotary speed-change-sensing mechanism, the combination as inclaim 6 in which the last-mentioned means comprises a pair of stationaryfulcrums each engageable with said arm to limit rocking of the latter inopposite directions on said eccentric.

8. In a rotary speed-change-sensing mechanism, the combination of:

a first rotary power transmission member adapted to be driven inrotation,

at second rotary member,

means providing a slip coupling between said members,

whereby said second member is adapted to be driven 16 in rotation bysaid first member and to slip with respect to said first member,

a first gyratory fulcrum,

means for turning said gyratory fulcrum independently of the secondrotary member,

a second oscillatory fulcrum carried on said second member foroscillatory movement with the latter member about its axis of rotation,

an arm rockably supported on said fulcrums in such manner that said armis adapted to be rocked on said second fulcrum by gyration of said firstfulcrum and the torque exerted on said second member by said firstmember during rotation of the latter in one direction tends to rock saidarm in a given direction on said first fulcrum, and

a stationary fulcrum engaging said arm to limit rocking of the latter insaid given direction on said ,first fulcrum, whereby said arm is rockedon said stationary fulcrum and said second fulcrum is oscillated bygyration of said first fulcrum and rotation of said first member in saidone direction in unison, and said arm is rocked on said second fulcrumout of engagement with said stationary fulcrum by gyration of said firstfulcrum during a reduction in the relative rotary speed of said firstmember with respect to the gyratory speed of said first fulcrum.

9. In a rotary speed-change-sensing mechanism, the

combination as in claim 8 which also includes drive means for drivingsaid first fulcrum in gyration and said first member in rotation in suchmanner that the rotary speed of said first member is adapted to bereduced independently of the gyratory speed of said first fulcrum inresponse to an overload on the system, and

control means operated by said arm upon rocking of the arm on saidsecond fulcrum out of engagement with said stationary fulcrum forcontrolling said system.

10. In a rotary speed-change sensing mechanism, the

combination as in claim 8 which also includes means including areversible power source for driving said first fulcrum in gyration andsaid first member in rotation in such manner that the rotary speed ofsaid first member is adapted to be reduced independently of the gyratoryspeed of said first fulcrum, and

means including a control device to be operated by said arm upon rockingof the arm on said fulcrum out of engagement with said stationaryfulcrum for deactivating said power source and conditioning the latterfor operation in the reverse direction.

11. In a rotary speed-change-sensing mechanism, the

combination as in claim 8 which also comprises a control device to beoperated by said arm upon rocking of the arm on said second fulcrum outof engagement with said stationary fulcrum.

[12. In a rotary speed-change-sensing mechanism, the

combination of:

a pair of rotary members,

an arm,

a stationary fulcrum engaging said arm,

a pair of independently movable fulcrums rockably supporting said armand movable in unison to rock said arm on said stationary fulcrum,

means including slip coupling means associated with one of said fulcrumsfor drivingly connecting said fulcrums individually to said respectiverotary members,

the relative speed of movement of one of said movable fulcrums withrespect to the other movable fulcrum being adapted to be changed,whereby movement of one movable fulcrum rocks said arm on the othermovable fulcrum out of engagement with said sta tionary fulcrum, and

a control device to be operated by said arm upon rock- 17 ing of saidarm out of engagement with said stationary fulcrum.]

[13. In a rotary speed-change-sensing mechanism, the

combination of:

an arm,

a stationary fulcrum engaging said arm,

a pair of independently movable fulcrums rockably supporting said armand movable in unison to rock said arm on said stationary fulcrum,

the relative speed of movement of one of said movable fulcrums withrespect to the other movable fulcrum being adapted to be changed,whereby movement of one movable fulcrum rocks said arm on the othermovable fulcrum out of engagement with said stationary fulcrum,

means for driving said pair of fulcrums, and

means to be operated by said arm upon rocking of the latter out ofengagement with said stationary fulcrum for controlling said drivingmeans] 14. A rotary speedchange-sensing mechanism, comprising incombination:

a first rotary member,

a second rotary member,

means providing a slip coupling between said two rtary members fordriving the second member from the first member while permitting theseond member to slip with respect to the first member,

an arm,

means establishing a normally stationary axis about which the arm canrock, said axis being shiftable between two positions,

a pair of spaced, independently movable fulcrums rockably supportingsaid arm and movable in unison to rock said arm about said axis, one ofsaid fulcrums providing a coupling between the first rotary member andthe arm, and

means including the other one of said fulcrums providing a couplingbetween the second rotary member and the arm,

the relative speed of movement of the movable fulcrums with respect toeach other being adapted to be changed whereby movement of one movablefulcrum rocks said arm about the other movable fulcrum to shift theposition of said axis.

15. A rotary speed-change-sensing mechanism as in claim 14 in which thepair of movable fulcrums comprises:

an oscillatory fulcrum, and

a gyratory fulcrum providing said coupling between the arm and therotary member.

16. A rotary speed-change-sensing mechanism, comprising in combination:

a first rotary member mounted to rotate about a first axis,

a second rotary member coaxial therewith,

means providing a slip coupling between said two rotary members fordriving the second member from the first member while permitting thesecond member to slip with respect to the first member,

an arm,

means establishing a second normally stationary axis about which the armcan rock, said second axis being shiftable between two positions,

an oscillatory fulcrum oscillating about the first axis and a gyratoryfulcrum turning about the first axis, said fulcrums being independentlymovable and rockably supporting said arm and being movable in unison torock said arm about said second axis, said gyratory fulcrum providing acoupling between the first rotary member and the arm, and

means providing a slip coupling between the second rotary member and theother one of said fulcrums whereby rotation of the second rotary memberbiases the oscillatory fulcrum independently of the second rotarymember,

the relative speed of movement of the movable fulcrums with respect toeach other being adapted to be changed whereby movement of one movablefulcrum rocks said arm about the other movable fulcrum to shift theposition of said second axis.

17. In a rotary speed-change-sensing mechanism, the

combination of:

a rotary shaft,

a first disc fixed to said shaft,

a second disc rotatable on said shaft,

first friction clutch means between said discs, whereby said second discis adapted to be driven in rotation by said first disc and to slip withrespect to said first disc,

a third disc rotatable on said shaft,

second friction clutch means between said third disc and said seconddisc, whereby, said third disc is adapted to be driven in rotation bysaid second disc and to slip with respect to said second disc,

an arm,

a pivotal coupling between said arm and said third disc,

an eccentric fixed to and rotating with said shaft and engaging said armto impart rocking motion to said arm,

the torque exerted on said third disc by said second disc duringrotation of the latter in one direction with said shaft tending to rocksaid arm in a given direction about said eccentric, and

means establishing a normally stationary axis about which the arm isrocked by said eccentric, the stationary axis being shiftable betweentwo positions by rocking motion of the arm about said pivotal coupling.

[18. A rotary speed-change-sensing mechanism, comprising in combination:

a first rotary member,

a second rotary member,

means providing a slip coupling between said two rotary members fordriving the second member from the first member while permitting thesecond member to slip with respect to the first member,

an arm,

means establishing a normally stationary axis about which the arm canrock, said axis being shiftable between two positions,

a pair of spaced, independently movable fulcrums rockably supportingsaid arm and movable in unison to rock said arm about said axis, one ofsaid fulcrums providing a coupling between the first rotary member andthe arm,

means including the other one of said fulcrums providing a couplingbetween the second rotary member and the arm,

the relative speed of movement of the movable fulcrums with respect toeach other being adapted to be changed whereby movement of one movablefulcrum rocks said arm about the other movable fulcrum to shift theposition of said axis,

motor means driving said rotary members, and

a control member operated by said arm upon shifting said axis betweensaid two positions to control said motor means] 19. The subject matterof claim 14, including motor means driving said rotary members, and

a control member operated by said arm upon shifting said axis betweensaid two positions to control said motor means.

20. In a safety device, the combination of:

an electric drive motor and a control circuit therefor including a:control switch,

a rotary slip clutch comprising a rotary input member powered by saidmotor and a rotary output member adapted to drive a mechanical load andto slip relative to said rotary input member when a predeterminedmechanical load is imposed thereon,

rotary cam means intercouplcd with said rotary input member of saidrotary slip clutch to turn consonantly therewith,

a mechanical oscillator coupled to said rotary cam means for oscillationthereby and including a switchactuating part for operating said controlswitch by a displacement movement relative to said oscillation, and

means having a friction slip coupling to said rotary output member ofsaid rotary slip clutch and an operative coupling to saidswitch-actuating part of said oscillator for effecting said displacementmovement of said switch-actuating part of said oscillator in response toarrest of said rotary output member of said clutch.

21. The subject matter of claim 20, wherein said oscillator includes anoscillatory lever,

means affording two alternate fulcrum points for said lever,

and wherein said means having said friction slip coupling to said rotaryoutput clutch member is arranged for application of a force to saidlever normally biasing said lever to pivot on one of said fulcrumpoints, and for coaction with said lever to cause pivoting thereof onthe other of said fulcrum points member of said rotary slip cluch toturn consonantly therewith,

a mechanical oscillator including an oscillatory lever,

a stationary knife edge fulcrum engaging said lever,

a coupling between said rotary cam means and a portion of said lever tooscillate said lever on said stationary fulcrum, and

means having a pivotal connection to a point on said lever spacedtherealong from said last mentioned portion thereof, said means having afriction slip coupling with said rotary output member of said rotaryslip clutch, and being arranged to transmit normally a bias torque tosaid lever in a direction to maintain said lever against said stationaryfulcrum, and to discontinue said bias in response to arrest of saidrotary output member of said rotary slip clutch and thereafter impose africtional drag on said lever in substitution for said bias torque,whereby said lever is rocked on said pivotal connection by said cammeans to separate from said stationary pivot.

References Cited The following references, cited by the Examiner, are ofrecord in the patented file of this patent or the original patent.

UNITED STATES PATENTS 1,459,757 6/1923 Stevenson 192-139 ORIS L. RADER,Primary Examiner K. L. CROSSON, Assistant Examiner US. Cl. X.R.

